Rapid calibration of 3D freehand ultrasound for vessel intervention

To create a freehand three-dimensional (3D) ultrasound (US) system for image-guided vessel interventions, a US probe calibration must be performed to build 3D volumes from 2D vessel images. In this paper, a novel calibration method of 3D freehand US is described. It simply images the tip of a tracked needle that could freely move around within the coupling medium while the probe is fixed. The physical coordinates of the tip and the probe location are simultaneously recorded. Image coordinates of the tip are mapped to physical points. A RANSAC algorithm is applied to minimize the error matching image points and physical points. An accuracy evaluation experiment is performed to verify the proposed method. Results show that the needle tip can be accurately located and the RMS calibration error is 1.56mm. A phantom experiment and an in vivo experiment verify the availability of the technique in clinic. That means the present method is applicable to the calibration of a 3D freehand US in vessel interventions.